Animation techniques involve creating a representation of a scene, including moving persons or things, and generating a moving picture of the scene as it changes over time. For example, cartoon animation generates a moving picture by creating hundreds or thousands of still pictures of the scene, each of which shows the scene in a different moment in time. When the still pictures are shown at an appropriate speed in chronological order, a lifelike moving picture is generated. More recently, much development has been done in the area of computer animation. Computer animated scenes involve less repetitive human hand drawing, and can be very lifelike.
One challenging aspect of animation is generating human faces as humans speak and portray different facial expressions. Various 2-dimensional (2D) and 3-dimensional (3D) animation techniques are currently used to create cartoons or video games. In general, it is difficult to scale the accuracy and efficiency of more complicated aspects of the animation, such as facial animation, using current techniques. For example, creating a highly accurate facial animation showing a human speaker using 3D methods may be possible, but may also be prohibitively expensive. It is also generally difficult to dynamically replay animation of, for example, a human speaker, and adjust the movement and sound speeds together accurately.